I tried to compile the package but:

<mavila@localhost dir="/home/mavila/hibernate-2.1"/> $ ant -version
Apache Ant version 1.6.1 compiled on February 12 2004

<mavila@localhost dir="/home/mavila/hibernate-2.1"/> $ java -version
java version "1.5.0-beta2"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-beta2-b51)
Java HotSpot(TM) Client VM (build 1.5.0-beta2-b51, mixed mode, sharing)


<mavila@localhost dir="/home/mavila/hibernate-2.1"/> $ ant
Buildfile: build.xml
[taskdef] Could not load definitions from resource clovertasks. It could not be found.

splash:

init:
[echo] Build Hibernate-2.1 (2004-08-01 03:55:49)
[mkdir] Created dir: /home/mavila/hibernate-2.1/build
[copy] Copying 9 files to /home/mavila/hibernate-2.1/build

compile:
[javac] Compiling 465 source files to /home/mavila/hibernate-2.1/build
[javac] /home/mavila/hibernate-2.1/src/net/sf/hibernate/Hibernate.java:189: as of release 1.5, 'enum' is a keyword, and may not be used as an identifier
[javac] (try -source 1.4 or lower to use 'enum' as an identifier)
[javac] public static Type enum(Class enumClass) throws MappingException {
[javac] ^
[javac] /home/mavila/hibernate-2.1/src/net/sf/hibernate/cfg/Configuration.java:385: as of release 1.5, 'enum' is a keyword, and may not be used as an identifier
[javac] (try -source 1.4 or lower to use 'enum' as an identifier)
[javac] Enumeration enum = jarFile.entries();
[javac] ^
[javac] /home/mavila/hibernate-2.1/src/net/sf/hibernate/cfg/Configuration.java:386: as of release 1.5, 'enum' is a keyword, and may not be used as an identifier
[javac] (try -source 1.4 or lower to use 'enum' as an identifier)
[javac] while( enum.hasMoreElements() ) {
[javac] ^
[javac] /home/mavila/hibernate-2.1/src/net/sf/hibernate/cfg/Configuration.java:388: as of release 1.5, 'enum' is a keyword, and may not be used as an identifier
[javac] (try -source 1.4 or lower to use 'enum' as an identifier)
[javac] ZipEntry ze = (ZipEntry) enum.nextElement();
[javac] ^
[javac] /home/mavila/hibernate-2.1/src/net/sf/hibernate/impl/AbstractQueryImpl.java:245: as of release 1.5, 'enum' is a keyword, and may not be used as an identifier
[javac] (try -source 1.4 or lower to use 'enum' as an identifier)
[javac] setParameter( position, val, Hibernate.enum( val.getClass() ) );
[javac] ^
[javac] /home/mavila/hibernate-2.1/src/net/sf/hibernate/impl/AbstractQueryImpl.java:305: as of release 1.5, 'enum' is a keyword, and may not be used as an identifier
[javac] (try -source 1.4 or lower to use 'enum' as an identifier)
[javac] setParameter( name, val, Hibernate.enum( val.getClass() ) );
[javac] ^
[javac] /home/mavila/hibernate-2.1/src/net/sf/hibernate/type/TypeFactory.java:169: as of release 1.5, 'enum' is a keyword, and may not be used as an identifier
[javac] (try -source 1.4 or lower to use 'enum' as an identifier)
[javac] type = Hibernate.enum(typeClass);
[javac] ^
[javac] 7 errors

BUILD FAILED
/home/mavila/hibernate-2.1/build.xml:145: Compile failed; see the compiler error output for details.

Total time: 4 seconds


Current solution, using previous version of the JSDK